To calculate the average marks, we first need to sum the marks obtained by all seven students in History and then divide by the total number of students.
Assume the marks obtained by the seven students in History are as follows:
\[
{Marks: } 80, 75, 70, 90, 85, 70, 60
\]
Step 1: Find the sum of the marks:
\[
{Sum of marks} = 80 + 75 + 70 + 90 + 85 + 70 + 60 = 570
\]
Step 2: Calculate the average by dividing the sum by the number of students (7):
\[
{Average} = \frac{570}{7} = 72.8571 \approx 72.86
\]
Thus, the average marks obtained by these seven students in History is \( 72.86 \).